Hi I am going to start putting up my ground floor internal walls soon. The back of my house is a single skin cavity block wall. The floor slab has been laid and the DPM is now just resting against this wall. My though is to build a block wall inside (one course high) then sit the stud wall on it with a layer of dpc in-between to stop rising damp. But what do I do with the DPM with is just resting on the wall. Do I tuck it over the new internal wall in-between the one course of blocks and stud footer.

Also, the builder who did my floor, did not put the drain under it when it was constructed they opted for a soak away in the back garden. This soak away was no more than a metre and a half away from the back wall of the house. Of course it rained real bad one day and the soak away filled up and the water came back in the house, about 4 inches covering 56 sqm metres. It is a mid-terrace conversion I m doing so no where else to run a drain. The reason it failed is the back garden where the soak away was comes down hill towards the house. God knows why the builders put it there. Anyway, they dug a channel in the new floor slab they had just laid to put a drain under the house, but as I was not there I don’t know weather when they cut the DPM they overlapped a new piece, or just put the old one back down as it was. I want to lay under floor heating and just in case they did not overlap it, I was going to put down a new DPM over the floor slab, then lay the insulation and under floor heating then the screed. Is this a good idea?

Boothy wrote:Hi I am going to start putting up my ground floor internal walls soon. The back of my house is a single skin cavity block wall. The floor slab has been laid and the DPM is now just resting against this wall. My though is to build a block wall inside (one course high) then sit the stud wall on it with a layer of dpc in-between to stop rising damp. But what do I do with the DPM with is just resting on the wall. Do I tuck it over the new internal wall in-between the one course of blocks and stud footer.

Also, the builder who did my floor, did not put the drain under it when it was constructed they opted for a soak away in the back garden. This soak away was no more than a metre and a half away from the back wall of the house. Of course it rained real bad one day and the soak away filled up and the water came back in the house, about 4 inches covering 56 sqm metres. It is a mid-terrace conversion I m doing so no where else to run a drain. The reason it failed is the back garden where the soak away was comes down hill towards the house. God knows why the builders put it there. Anyway, they dug a channel in the new floor slab they had just laid to put a drain under the house, but as I was not there I don’t know weather when they cut the DPM they overlapped a new piece, or just put the old one back down as it was. I want to lay under floor heating and just in case they did not overlap it, I was going to put down a new DPM over the floor slab, then lay the insulation and under floor heating then the screed. Is this a good idea?

nail the dpm to the external wall at least 225mm high using galvanised nails.
lay dpc on the floor underneath your base stud internally and fix to the concrete.
they should have taped the dpm where its cut,But if you want to make sure its sealed paint the floor with a bitumin paint.
for the surface water problem use ACO drainage system along the back of your property and connect it to the pipe